We meet where they killed a man. Budding writer Brent Taylor was working late at the University of Auckland library when he was attacked, his skull bouncing and vertebrae popping as he tumbled down the stairs.

Linda Olsson and Thomas Sainsbury smile widely as they shake my hand. They may not have personally shovelled the troubled young man's body over the guardrail, but they planned his death. And he won't be their final murder; they're just getting started ...